1. Technical Field
The present specification relates to a power supply device that is applied to a vehicle in which a generator motor is mounted as a drive source for generating drive power of the vehicle and that includes a battery capable of charging and discharging, a converter, and an inverter.
2. Description of Related Art
In a power supply device that includes a converter and an inverter, each of which is configured by including a switching element, there is a case where an overvoltage as a voltage that is at least equal to a specified threshold is generated in a primary-side voltage (a low-voltage-side voltage) and/or a secondary-side voltage (a high-voltage-side voltage) of the power supply device. A power supply device for executing protection control in which each of the switching elements of the converter and the inverter is forcibly stopped (hereinafter also referred to as “shut down”) so as to prevent equipment breakdown inside and outside of the power supply device at a time when the overvoltage is generated has been known. This converter has: an upper arm that includes the switching element; and a lower arm that is connected to the upper arm in series and includes the switching element, increases the primary-side voltage applied from a battery by switching the switching element of the lower arm, and applies the increased voltage as the secondary-side voltage to the inverter. In addition, this converter lowers the secondary-side voltage by switching the switching element of the upper arm and applies the lowered voltage as the primary-side voltage to the battery.
When each of the switching elements of the converter and the inverter is shut down by the above protection control, the secondary-side voltage of the power supply device is lowered due to power consumption by discharge resistance in a high-pressure-side circuit (a circuit operated by the secondary-side voltage). Alternatively, the primary-side voltage of the power supply device is lowered due to power consumption by auxiliary machines that are connected to a low-voltage-side circuit (a circuit operated by the primary-side voltage).
In view of the above, in one of conventional power supply devices (hereinafter referred to as a “conventional device”), in the case where the above secondary-side voltage and/or the above primary-side voltage is lowered and it is determined that states of the power supply device, peripheral circuits, and the like allow a vehicle to travel in a limp home mode, each of the switching elements of the converter is shut down. In this way, the vehicle travels in the limp home mode only by power discharged from the battery.
Furthermore, in a case of failure of an overvoltage determination circuit that determines whether the overvoltage is generated in the converter, an overvoltage signal indicating that the primary-side voltage has exceeded the specified threshold is occasionally generated. Also, in this case, similar to a time when the overvoltage is generated, the conventional device shuts down each of the switching elements of the converter and the inverter. Thereafter, if it is determined that the vehicle is allowed to travel in the limp home mode, the vehicle travels in the limp home mode only by power discharged from the battery.
By utilizing this method, the conventional device directly applies a DC voltage that is output from the battery to the inverter without increasing the voltage. Furthermore, the conventional device causes the inverter to convert this DC voltage to an AC voltage, drives a generator motor, and allows the vehicle to travel in the limp home mode by which the vehicle can move to a safe place (for example, see Japanese Patent Application Publication No. 2009-201195 (JP 2009-201195 A)).
However, the inverter is operated by the voltage (the voltage of the battery) that is not increased by the converter during the above limp home mode travel of the vehicle. Accordingly, the AC voltage output by the inverter is lower than that during normal travel. Thus, the conventional device may not be able to obtain sufficient drive power by the generator motor during the limp home mode travel.